Spark ignition circuit



Dec. 5, 1967 N. A. JUKE S SPARK IGNITION CIRCUIT Filed Nov. 4, 1965 United States Patent 3,356,082 SPARK IGNITION CIRCUIT Norman Alfred Jukes, Walsall, England, assignor to Joseph Lucas (Industries) Limited, Birmingham,

England Filed Nov. 4, 1965, Ser. No. 506,357

Claims priority,

1 Claim. (Cl. 123102) ABSTRACT OF THE DISCLOSURE value.

This invention relates to spark ignition circuits, and in its broad The accompanying drawing is a circuit diagram illustrating one example of the invention.

Referring to the drawing, there is provided a magnetic pick-up winding 11 which is associated with the starter to the line 17 through a resistor 36, and its collector connected to the terminal 13 through a resistor 37. The collector of the transistor 33 is further connected through resistors 38, 39 in series to the line 17, a point intermediate the resistors 33, 39 being connected to the base of a transistor 41 having its emitter connected to the emitter of the transistor 33 and its collector connected to the application Great Britain, Dec. 2, 1964, v

terminal 13 through a resistor 42 and also connected to the base of a transistor 43. The transistor 43 has its emitter connected to the terminal 13, and its collector connected to the terminal 14 through resistors 44, 45 in series With the ignition switch 19. A point intermediate the resistors 44, 45 is connected to the gate of a controlled rectifier 46 the cathode of which is connected to the terminal 14 through the switch 19, and the anode of which is connected to the terminal 13 through the primary winding 47 of an ignition transformer 48 and a contact breaker 49 in series. The contact breaker 49 is bridged by a capacitor 51 in the usual way, and the secondary winding 52 of the ignition coil is connected through a distributor to the spark plugs of the engine in turn. The supply between the terminal 13 and line 17 is stabilised by a Zener diode 53.

In use, pulses are developed in the winding 11 at a frequency proportional to engine speed. The capacitors 16, 21 are not both essential, but their inclusion enables the circuits to be used for positive or negative earth systems. The output from the winding 11 is in the form of a sine wave and the transistors 23, 27 and their associated components form an amplifier in which positive feedback is provided by way of the resistor 26, this amplifier serving to convert the sine wave to a square wave form which appears across the resistor 28. A variable proportion of engine speed.

As long as the speed of the engine is below a predetermined value, the bistable circuit constituted by the transistors 33, 41 and their associated components operates in its state in which the transistor 41 conducts, so that base current is supplied to the transistor 43, which also conducts. Conduction of the transistor 43 causes a positive gate-cathode current to flow in the rectifier 46, which therefore conducts. When the contact breaker is closed, current builds up in the winding 47 in the normal way, and when the contact breaker 49 opens, a spark is produced, When the contact breaker 49 closes again, the rectifier 46 will conduct again because it is still supplied with gate-cathode current.

When the speed of the engine rises above a predetermined value which can be altered by altering the variable on the resistor 28, the voltage across the capacitor 34 reaches a value at which it causes the transistor 33 to conduct, whereupon the bistable circuit is driven to its alternative state in which the transistor 41 ceases to con duct, so that no base current is supplied to the transistor 43. The rectifier 46 now conducts only until the contact breaker 49 opens, because when the contact breaker 49 closes again, there is no gate-cathode current flow in the rectifier 46, and so the circuit of the primary winding 47 is not completed.

The circuit described has the advantage that because the pulses derived from the ring 12 have a high frequency, there will be very little speed overshoot before the rectifier 46 stops sparks from being supplied to the plugs.

The circuit described can be utilised in road vehicles or in other applications, for example in motorboats.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

A spark ignition circuit for use with an internal combustion engine having spark plugs and a toothed starter gear ring, comprising in combination an ignition transformer having a primary winding and a secondary winding, said ignition transformer producing sparks at said plugs 1n turn, a magnetic pick-up winding associated with said starter gear ring, said starter gear ring producing References Cited. UNITED STATES PATENTS 2,957,135 10/1960 Gray 324-70 X 5 3,116,596 1/1964 Boehme 60---30 3,153,746 10/1964 Atkinson 3175 3,182,648 5/1965 Schneider 123*"1'148 3,3 14,407 4/ 1967 Schneider 10 RALPH D. BLAKESLEE, Primary Emma 

